• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2001.04a
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• pp.441-446
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• 2001

This paper presents the thermal characteristics analysis of a high-speed HMC spindle system with angular contact ball bearings, built-in motor, oil-jet lubrication method, oil jacket cooling method, and so on. The spindle system is composed of the main spindle and sub-spindle which are mechanically connected by a flexible coupling. The spindles are supported by two front and rear bearings, and the built-in motor is located between the front and rear bearings of the sub-spindle. The thermal analysis model of spindle system is constructed by the finite element method, and the thermal characteristics in the design stage are estimated based on temperature distribution and heat flow under the various testing conditions related to material of bearing ball, spindle speed and coolant temperature.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.79-83
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• 2001

A cone-shaped active magnetic bearing spindle system for high speed internal grinding is designed and tested. The cone-shaped AMB system consists of only 4 couples of magnet, it can be smaller and lighter than conventional radial-axial-type AMB system. In this paper, the cone-shaped electromagnets are designed by magnetic circuit theory, and de-coupled direct feedback PID controller is applied to control the coupled magnetic bearings. The designed cone-shaped AMB spindle system is built and constructed with a digital control system, and tested its stbility and dynamic performances. As the results of the tests, this spindle runs up to 40,000 rpm with about 5 ${\mu}{\textrm}{m}$ of runout, and the AMB system provides high damping ratio eliminating overshoot and resonance speed.

• Journal of KSNVE
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• v.5 no.4
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• pp.483-492
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• 1995

For evaluation of rotational accuracy performance of high speed machine tool spindle system, the characteristics of main spindle and tool motion behavior are presented by means of three point accuracy testing method. The results of experiments and analyses are as follows: (1) The high speed spindle rotational accuracy can be evaluated by the combination of the spindle and tool motion behavior. (2) The spindle motion behavior increases up to more that 4 times the tool motion behavior. (3) For the influence of oil viscosity on spindle and tool taper application, 32 cSt of oil viscosity showed the most satisfactory result for rotational accuracy. (4) In order to improve the rotational accuracy of high speed machine tool spindle system, it is needed to reduce the combination error. This can be achieved by improving the working accuracy and supplying the proper lubrication with contact area at the spindle and tool.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1640-1643
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• 2005

This paper presents analysis of dynamic characteristics of a high-speed milling spindle with a drawbar and a built-in motor. The spindle system with a built-in motor can be used to simplify the structure of machine tools, to improve the machining flexibility of machine tools, and to perform the high speed machining. In this system the shaft is usually assumed as a rigid rotor. In this paper, the modal characteristics of drawbar in high-speed milling spindle system due to supporting stiffness between drawbar and shaft and considering the mass and stiffness effects of the built-in motor's rotor are analyzed by numerical method. The result shows enough stiff supports must be provided between shaft and drawbar to prevent occurring drawbar vibration lower than the natural frequency of 1st bending mode of spindle. And considering the mass and stiffness of built-in motor's rotor is important thing to derive more accurate results.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.2
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• pp.213-219
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• 2002

A cone-shaped active magnetic healing spindle system for high speed internal grinding with built-in motor that has 7.5kW power and maximum rotational speed of 50,000 rpm is designed and built. Using cone-shaped AMB(Active Magnetic Bearing) system, the axial rotor dick and magnets of conventional 5-axis actuating design can be eliminated. so this concept of design provides a simple magnetic bearing system. In this paper, the cone-shaped electromagnets are designed by magnetic circuit theory, and a de-coupled direct feedback PID controller is applied to control the coupled magnetic bearings. The designed crone-shaped AMB spindle system is built and constructed with a digital control system, which has TMS320C6702 DSP, 16 bit AD/DA, switching power amplifier and gap sensors. As the AMB system provides high damping ratio eliminating overshoot and resonance speed, this spindle runs up to 40,000 rpm stably with about 5${\mu}{\textrm}{m}$ of runout.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.13 no.3
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• pp.83-88
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• 2014

FSI (Fluid Structure Interaction) method, in this study, has been applied to analyzing thermal characteristics of a high speed machine tool spindle system. The spindle is composed of angular contact ceramic ball bearings, a high speed built-in motor, a cooling jacket, and so on. The cooling jacket has three inlets and outlets. Using the FSI method, temperature distributions and thermal displacements of the spindle system were computed considering the heating of the front and rear bearings and the built-in motor. The results computed using the FSI method were compared with those determined by experiment and using the conventional numerical approach. The results determined using the FSI method were similar to those from the conventional numerical approach but showed better agreement with the experimental results. Therefore, it is concluded that the FSI method is useful for analyzing the thermal characteristics of high speed spindles and can be applied to the design of high speed spindles.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.5
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• pp.20-25
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• 2011

In this paper, we reviewed the spindle system's motor and bearing and its mode safety for optimal design of a high speed spindle system that exceeds DmN value of 1,500,000. We could verify that it has a separation margin during critical speed by performing critical speed analysis. Also, we have selected an optimal sensoring installation location and actually manufactured & installed the sensor by identifying the stress concentration position in the axial load through finite element analysis to install the built-in piezo electric type load sensor to the spindle housing that can measure and monitor the machining load during high speed rotation of the spindle. Reproducibility is also verified by calibrating the error through the sensor's sensitivity adjustment after comparing the output between the plate dynamoneters and the load sensor to confirm the reproducibility of the load sensor.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.14 no.6
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• pp.31-36
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• 2005

Use of the high frequency motor spindles are increasing for the high speed machine tools recently. The important problem in the high speed spindles is to reduce and minimize the thermal effect by the motor and ball hearings. Thermal characteristics according to the bearing preload and spindle cooling are studied for the spindle with the oil mist lubrication and high frequency motor. Temperature distribution and thermal displacement according to the spindle speed, preload and flow rate are measured. Temperature distribution and thermal displacement of the high speed spindle system can be estimated reasonably by using the three dimensional model through the finite element method. The results of analysis are compared with the measured data. This study supports thermal optimization and find out more effective cooling condition. This paper show that the suitable preload and spindle cooling are very effective to minimize the thermal effect by the motor and ball bearings.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.5
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• pp.108-114
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• 2007

A new cutting force estimating approach and machining state monitoring examples are presented which uses a cylindrical displacement sensor built into the spindle. To identify the tool-spindle system dynamics with frequency up to 2 kHz, a home-built electro-magnetic exciter is used. The result is used to build an algorithm to extract the dynamic cutting force signal from the spindle error motion; because the built-in spindle sensor signal contains both spindle-tool dynamics and tool-workpiece interactions. This sensor is very sensitive and can measure broadband signal without affecting the system dynamics. The main characteristic is that it is designed so that the measurement is irrelevant to the geometric errors by covering the entire circumferential area between the target and sensor. It is also very simple to be installed. Usually the spindle front cover part is copied and replaced with a new one with this sensor added. It gives valuable information about the operating condition of the spindle at any time. It can be used to monitor cutting force and chatter vibration, to predict roughness and to compensate the form error by overriding spindle speed or feed rate. This approach is particularly useful in monitoring a high speed machining process.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.5 no.4
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• pp.90-97
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• 1996

The thermal deformation of a machine tool spindle influences the performance of the manufacturing systems for precision products. In this research, thermal analysis of a high speed machine tool spindle with the rolling bearing and the built-in motor is carried out by using Finite Difference Method. The thermal boundary conditions describing the heat generation in the bearing and built-in motor are considered in the simulation. And various convective boundary conditions are assumed with the empirical formula in the references. From the simulation results, the characteristics of each element affecting the dynamic thermal behaviour of the machine tool spindle system have been clarified. Therefore, this model can be well applied to the future development of the high speed spindle systems.